R. Bastiaans - Academia.edu (original) (raw)

Papers by R. Bastiaans

International Journal of Heat and Fluid Flow, 2020

This paper focuses on the effects of a space-time dependent periodic stirring of a moderately tur... more This paper focuses on the effects of a space-time dependent periodic stirring of a moderately turbulent planar coflow jet configuration. The baseline flow is agitated in time and in space by small-scale turbulent perturbations in combination with large-scale modulation imposed at the inflow plane of a rectangular domain of size L × L × 2L in the x, y and z directions respectively. The prescribed large-scale modulation is characterized by a single modulation frequency ω and modulation wave-number, K. A parametric study at different modulation frequencies and wave-numbers is performed. We evaluate the system response to the external agitation in terms of key dynamic properties of the flow, e.g., the total kinetic energy E T , the global averaged dissipation rate and additional flow mixing properties. For low modulation frequencies, e.g., = 0.5 , 0 where ω 0 is the large scaleturn over frequency, = U D / , 0 1 with U 1 and D being relevant velocity and length scales, and at given wavenumber K, we observe that E T follows the imposed oscillation with a periodic amplitude response that is sustained at locations further from the inflow plane, whereas for higher frequencies, the response amplitude rapidly decays. Results of the global dissipation rate show the development of a definite maximum value of the response amplitude at frequencies on the order of ω 0 for any modulation wave-number K. To investigate in more detail the effects of modulated turbulence on the jet mixing properties, a passive scalar was injected at the inflow plane. The spreading of the scalar surface in the agitated jet was monitored for a wide range of modulation frequencies. In general, results show enhanced mixing efficiency when the main jet is modulated at frequencies near ω 0 and low K values.

Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emis... more Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emissions the main source of greenhouse gas (GHGs) emissions. Recently, ammonia (NH3) has gained attention as a potential carbon-free energy vector (carrier). NH3 can be produced from waste sources, renewable energy, coupled with already existing infrastructures for production and distribution. However, pure NH3 suffers from low flame speed and potentially important nitrogen oxide (NOx) emissions. As such, blending fuels such as methane (CH4) or hydrogen (H2) with NH3 could potentially address NH3's poor combustion capacities. Therefore, the program FLEXnCONFU has been conceived, supporting bespoke research to tackle some of the fundamental and applied challenges of using these blends. This paper addresses some of the current FLEXnCONFU's progress. Firstly, a series of experiments using a spherical expanding flame setup was employed to investigate potential increases in reactivity of NH3 and its blends with H2 and CH4. Secondly, direct numerical simulation (DNS) modelling of NH3/H2 turbulent expanding spherical flames was performed at lean and rich conditions. Finally, this study also discusses experimental results from an industrial scale swirl burner with varying content of CH4/NH3/H2 under rich condition (Φ = 1.2), in terms of radicals and exhaust emissions. The work is a step towards using non-conventional fuels such as NH3 and H2 and scaling up the technology from lab to industrial level.

Flamelet Generated Manifolds (FGM) has been extended to account for preferential diffusion effect... more Flamelet Generated Manifolds (FGM) has been extended to account for preferential diffusion effects and autoignition. Such development is made in order to study stabilization mechanism of turbulent lifted CH4/H2 flames of the Delft JHC burner. In this burner, methane based fuel has been enriched from 0 to 25% of H2. The main stabilization mechanism of these turbulent flames is autoignition based on the formation of ignition kernels which is very challenging to model. Addition of hydrogen makes the modeling even more challenging due to preferential diffusion effects. The proposed FGM model is implemented in DNS of unsteady mixing layer and LES of lifted jet flames. It is revealed that the proposed model has the capability to accurately predict main features of CH4/H2 turbulent flames.

Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines

Within the context of an ever-increasing share of wind, solar and emerging tidal power, the need ... more Within the context of an ever-increasing share of wind, solar and emerging tidal power, the need to store energy, not only on the short term, but also in the medium to long-term to balance out the power grid will become more important in the near future. One of the most promising routes for this mid- to long term storage, is to produce hydrogen through electrolysis using excess electricity and store it. Instead of using this hydrogen then to generate electricity in a conventional, large, power plant, a more efficient route is to use it in a Decentralised Energy System (DES) using micro Gas Turbines (mGTs). Although the mGT presents itself as a promising option to convert pure hydrogen into electricity in this DES framework, several challenges, linked to the necessary increase of Turbine Inlet Temperature (TIT) for efficiency increase to make the unit compatible and the use of pure hydrogen in the combustor, still need to be overcome. In this paper we present the first steps towards ...

Volume 3: Cycle Innovations; Education; Electric Power; Fans and Blowers; Industrial and Cogeneration, 2012

ABSTRACT Currently, high efficiency and low emissions are most important requisites for the desig... more ABSTRACT Currently, high efficiency and low emissions are most important requisites for the design of modern gas turbines due to the strong environmental restrictions around the world. In the past years, alternative fuels have been considered for application in industrial gas turbines. Therefore, combustor performance, pollutant emissions and the ability to burn several fuels became of much concern and high priority has been given to the combustor design.This paper describes a methodology focused on the design of stationary gas turbines combustion chambers with the ability to efficiently burn conventional and alternative fuels. A simplified methodology is used for the calculations of the equilibrium temperature and chemical species in the primary zone of a gas turbine combustor. Direct fuel injection and diffusion flames, together with numerical methods like Newton-Raphson, LU Factorization and Lagrange Polynomials, are used for the calculations. Diesel, ethanol and methanol fuels were chosen for the numerical study.A computer code sequentially calculates the main geometry of the combustor. From the numerical simulation it is concluded that the basic gas turbine combustor geometry, for some operating conditions and burning diesel, ethanol or methanol, are of similar sizes, because the development of aerodynamic characteristics predominate over the thermochemical properties.It is worth to note that the type of fuel has a marked effect on the stability and combustion advancement in the combustor. This can be seen when the primary zone is analyzed under a steady-state operating condition. At full power, the pressure is 1.8 MPa and the temperature 1,000 K at the combustor inlet. Then, the equivalence ratios in the primary zone are 1.3933 (diesel), 1.4352 (ethanol) and 1.3977 (methanol) and the equilibrium temperatures for the same operating conditions are 2,809 K (diesel), 2,754 K (ethanol) and 2,702 K (methanol). This means that the combustor can reach similar flame stability conditions, whereas the combustion efficiency will require richer fuel/air mixtures of ethanol or methanol are burnt instead of diesel.Another important result from the numerical study is that the concentration of the main pollutants (CO, CO2, NO, NO2) is reduced when ethanol or methanol are burnt, in place of diesel.

Combustion Science and Technology

Flow, Turbulence and Combustion

Numerical simulations are foreseen to provide a tremendous increase in gasturbine burners efficie... more Numerical simulations are foreseen to provide a tremendous increase in gasturbine burners efficiency in the near future. Modern developments in numerical schemes, turbulence models and the consistent increase of computing power allow Large Eddy Simulation (LES) to be applied to real cold flow industrial applications. However, the detailed simulation of the gas-turbine combustion process remains still prohibited because of its enormous computational cost. Several numerical models have been developed in order to reduce the costs of flame simulations for engineering applications. In this paper, the Flamelet-Generated Manifold (FGM) chemistry reduction technique is implemented and progressively extended for the inclusion of all the combustion features that are typically observed in stationary gas-turbine combustion. These consist of stratification effects, heat loss and turbulence. Three control variables are included for the chemistry representation: the reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the stratification effect is expressed by the mixture fraction. The interaction between chemistry and turbulence is considered through a presumed beta-shaped probability density function (PDF) approach, which is considered for progress variable and mixture fraction, finally attaining a 5-D manifold. The application of FGM in combination with heat loss, fuel stratification and turbulence has never been studied in literature. To this aim, a highly turbulent and swirling flame in a gas turbine combustor is computed by means of the present 5-D FGM implementation coupled to an LES turbulence model, and the results are compared with experimental data. In general, the model gives a rather good agreement with experimental data. It is shown that the inclusion of heat loss strongly enhances the temperature predictions in the whole burner and leads to greatly improved NO predictions. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable A. Donini Flow Turbulence Combust (2017) 98:887-922 computational effort. The implemented combustion model retains most of the physical accuracy of a detailed simulation while drastically reducing its computational time, paving the way for new developments of alternative fuel usage in a cleaner and more efficient combustion.

Proceedings of the Combustion Institute

New laminar burning velocity measurements of 85:15% (by volume) H 2 -CO and H 2 -N 2 mixtures wit... more New laminar burning velocity measurements of 85:15% (by volume) H 2 -CO and H 2 -N 2 mixtures with O 2 -He oxidizer are reported at lean conditions and elevated pressures (1-10 atm). Experiments are conducted using the heat flux method at initial temperature of 298 K. In this technique a near adiabatic flame is stabilized by balancing the heat loss from the flame to the burner with heat gain to the unburnt gas mixture such that no net heat loss to the burner is observed. A new facility was designed for such high pressure burner stabilized flame experiments. The results obtained are compared with five chemical kinetic schemes from literature for syngas mixtures at elevated pressures. Large differences are observed between the kinetic schemes and the experiments which can be attributed to certain key chemical reactions. A study of the kinetics is performed through reaction rate and sensitivity analysis which indicate that a high uncertainty still remains in important reactions that drive the production and consumption of species such as H, HO 2 and OH. For lean mixtures the reaction H + O 2 (+M) = HO 2 (+M) contributes significantly to the deviation of models from the experiments. The present analysis in the lean mixture regime suggests the need for further studies in assessment and modification of rate constants for this reaction.

Proceedings of the Combustion Institute

ABSTRACT CFD predictions of flame position, stability and emissions are essential in order to obt... more ABSTRACT CFD predictions of flame position, stability and emissions are essential in order to obtain optimized combustor designs in a cost efficient way. However, the numerical modeling of practical combustion systems is a very challenging task. As a matter of fact, the use of detailed reaction mechanisms is necessary for reliable predictions, especially for highly diffusive fuels. Unfortunately, the modeling of the full detail of practical combustion equipment is currently prohibited by the limitations in computing power, given the large number of species and reactions involved. The Flamelet Generated Manifold (FGM) method reduces these computational costs by several orders of magnitude without loosing too much accuracy. Hereby, FGM enables the application of reliable chemistry mechanisms in CFD simulations of combustion processes. In the FGM technique the progress of the flame is generally described by a few control variables. For each control variable a transport equation is solved during run-time. The flamelet system is computed in a pre-processing stage, and a manifold with all the information about combustion is stored in a tabulated form. In the present paper, the FGM model is implemented for the analysis of partially premixed non-adiabatic flames, including the effects of differential diffusion. Subsequently, a computational analysis of partially premixed non-adiabatic flames is presented. In this scope, a series of test simulations is performed using FGM for a two dimensional geometry, characterized by a distinctive stratified methane/air inlet, and compared with detailed chemistry simulations. The results indicate that detailed simulations are well reproduced with the FGM technique.

Ercoftac Series, 2000

The accuracy of large-eddy simulation (LES) of a turbulent premixed Bunsen flame is investigated ... more The accuracy of large-eddy simulation (LES) of a turbulent premixed Bunsen flame is investigated in this paper. To distinguish between discretization and modeling errors, multiple large-eddy simulations, using different grid size h but the same filterwidth Δ, are compared with the direct numerical simulation (DNS). In addition, large-eddy simulations using multiple Δ but the same ratio Δ/h are compared. The

Flow, Turbulence and Combustion, 2015

In this report we investigate the performance of particle tracking, exploring the influence of an... more In this report we investigate the performance of particle tracking, exploring the influence of an increasing amount of estimators. Basically, a simple method to determine particle matchings was used. Then, first, temporal extrapolation as well as spatial interpolation are employed. Second, a PIV processing step was incorporated. Tests from simulations show that at relatively high seeding densities the performance was increased with a factor of 4 and 13 for the first and second step, respectively. In a physical experiment of a wake behind a heated cylinder a clear performance improvement in the case of PIV preprocessing was observed.

Journal of Engineering for Gas Turbines and Power, 2014

In the present paper, a computational analysis of a high pressure confined premixed turbulent met... more In the present paper, a computational analysis of a high pressure confined premixed turbulent methane/air jet flames with heat loss to the walls is presented. In this scope, chemistry is reduced by the use of the flamelet generated manifold (FGM) method and the fluid flow is modeled in an large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) context. The reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. A generic lab scale burner for methane high-pressure (5 bar) high-velocity (40 m/s at the inlet) preheated jet is adopted for the simulations, because of its gas-turbine relevant conditions. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort. Furthermore, the present analysis indicates that the physical a...

ABSTRACT In the present paper a computational analysis of a high pressure confined premixed turbu... more ABSTRACT In the present paper a computational analysis of a high pressure confined premixed turbulent methane/air jet flames is presented. In this scope, chemistry is reduced by the use of the Flamelet Generated Manifold method [1] and the fluid flow is modeled in an LES and RANS context. The reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. The interaction between chemistry and turbulence is considered through a presumed probability density function (PDF) approach. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort. Furthermore, the present analysis indicates that the physical and chemical processes controlling carbon monoxide (CO) emissions can be captured only by means of unsteady simulations.

International Journal of Heat and Fluid Flow, 2020

This paper focuses on the effects of a space-time dependent periodic stirring of a moderately tur... more This paper focuses on the effects of a space-time dependent periodic stirring of a moderately turbulent planar coflow jet configuration. The baseline flow is agitated in time and in space by small-scale turbulent perturbations in combination with large-scale modulation imposed at the inflow plane of a rectangular domain of size L × L × 2L in the x, y and z directions respectively. The prescribed large-scale modulation is characterized by a single modulation frequency ω and modulation wave-number, K. A parametric study at different modulation frequencies and wave-numbers is performed. We evaluate the system response to the external agitation in terms of key dynamic properties of the flow, e.g., the total kinetic energy E T , the global averaged dissipation rate and additional flow mixing properties. For low modulation frequencies, e.g., = 0.5 , 0 where ω 0 is the large scaleturn over frequency, = U D / , 0 1 with U 1 and D being relevant velocity and length scales, and at given wavenumber K, we observe that E T follows the imposed oscillation with a periodic amplitude response that is sustained at locations further from the inflow plane, whereas for higher frequencies, the response amplitude rapidly decays. Results of the global dissipation rate show the development of a definite maximum value of the response amplitude at frequencies on the order of ω 0 for any modulation wave-number K. To investigate in more detail the effects of modulated turbulence on the jet mixing properties, a passive scalar was injected at the inflow plane. The spreading of the scalar surface in the agitated jet was monitored for a wide range of modulation frequencies. In general, results show enhanced mixing efficiency when the main jet is modulated at frequencies near ω 0 and low K values.

Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emis... more Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emissions the main source of greenhouse gas (GHGs) emissions. Recently, ammonia (NH3) has gained attention as a potential carbon-free energy vector (carrier). NH3 can be produced from waste sources, renewable energy, coupled with already existing infrastructures for production and distribution. However, pure NH3 suffers from low flame speed and potentially important nitrogen oxide (NOx) emissions. As such, blending fuels such as methane (CH4) or hydrogen (H2) with NH3 could potentially address NH3's poor combustion capacities. Therefore, the program FLEXnCONFU has been conceived, supporting bespoke research to tackle some of the fundamental and applied challenges of using these blends. This paper addresses some of the current FLEXnCONFU's progress. Firstly, a series of experiments using a spherical expanding flame setup was employed to investigate potential increases in reactivity of NH3 and its blends with H2 and CH4. Secondly, direct numerical simulation (DNS) modelling of NH3/H2 turbulent expanding spherical flames was performed at lean and rich conditions. Finally, this study also discusses experimental results from an industrial scale swirl burner with varying content of CH4/NH3/H2 under rich condition (Φ = 1.2), in terms of radicals and exhaust emissions. The work is a step towards using non-conventional fuels such as NH3 and H2 and scaling up the technology from lab to industrial level.

Flamelet Generated Manifolds (FGM) has been extended to account for preferential diffusion effect... more Flamelet Generated Manifolds (FGM) has been extended to account for preferential diffusion effects and autoignition. Such development is made in order to study stabilization mechanism of turbulent lifted CH4/H2 flames of the Delft JHC burner. In this burner, methane based fuel has been enriched from 0 to 25% of H2. The main stabilization mechanism of these turbulent flames is autoignition based on the formation of ignition kernels which is very challenging to model. Addition of hydrogen makes the modeling even more challenging due to preferential diffusion effects. The proposed FGM model is implemented in DNS of unsteady mixing layer and LES of lifted jet flames. It is revealed that the proposed model has the capability to accurately predict main features of CH4/H2 turbulent flames.

Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines

Within the context of an ever-increasing share of wind, solar and emerging tidal power, the need ... more Within the context of an ever-increasing share of wind, solar and emerging tidal power, the need to store energy, not only on the short term, but also in the medium to long-term to balance out the power grid will become more important in the near future. One of the most promising routes for this mid- to long term storage, is to produce hydrogen through electrolysis using excess electricity and store it. Instead of using this hydrogen then to generate electricity in a conventional, large, power plant, a more efficient route is to use it in a Decentralised Energy System (DES) using micro Gas Turbines (mGTs). Although the mGT presents itself as a promising option to convert pure hydrogen into electricity in this DES framework, several challenges, linked to the necessary increase of Turbine Inlet Temperature (TIT) for efficiency increase to make the unit compatible and the use of pure hydrogen in the combustor, still need to be overcome. In this paper we present the first steps towards ...

Volume 3: Cycle Innovations; Education; Electric Power; Fans and Blowers; Industrial and Cogeneration, 2012

ABSTRACT Currently, high efficiency and low emissions are most important requisites for the desig... more ABSTRACT Currently, high efficiency and low emissions are most important requisites for the design of modern gas turbines due to the strong environmental restrictions around the world. In the past years, alternative fuels have been considered for application in industrial gas turbines. Therefore, combustor performance, pollutant emissions and the ability to burn several fuels became of much concern and high priority has been given to the combustor design.This paper describes a methodology focused on the design of stationary gas turbines combustion chambers with the ability to efficiently burn conventional and alternative fuels. A simplified methodology is used for the calculations of the equilibrium temperature and chemical species in the primary zone of a gas turbine combustor. Direct fuel injection and diffusion flames, together with numerical methods like Newton-Raphson, LU Factorization and Lagrange Polynomials, are used for the calculations. Diesel, ethanol and methanol fuels were chosen for the numerical study.A computer code sequentially calculates the main geometry of the combustor. From the numerical simulation it is concluded that the basic gas turbine combustor geometry, for some operating conditions and burning diesel, ethanol or methanol, are of similar sizes, because the development of aerodynamic characteristics predominate over the thermochemical properties.It is worth to note that the type of fuel has a marked effect on the stability and combustion advancement in the combustor. This can be seen when the primary zone is analyzed under a steady-state operating condition. At full power, the pressure is 1.8 MPa and the temperature 1,000 K at the combustor inlet. Then, the equivalence ratios in the primary zone are 1.3933 (diesel), 1.4352 (ethanol) and 1.3977 (methanol) and the equilibrium temperatures for the same operating conditions are 2,809 K (diesel), 2,754 K (ethanol) and 2,702 K (methanol). This means that the combustor can reach similar flame stability conditions, whereas the combustion efficiency will require richer fuel/air mixtures of ethanol or methanol are burnt instead of diesel.Another important result from the numerical study is that the concentration of the main pollutants (CO, CO2, NO, NO2) is reduced when ethanol or methanol are burnt, in place of diesel.

Combustion Science and Technology

Flow, Turbulence and Combustion

Numerical simulations are foreseen to provide a tremendous increase in gasturbine burners efficie... more Numerical simulations are foreseen to provide a tremendous increase in gasturbine burners efficiency in the near future. Modern developments in numerical schemes, turbulence models and the consistent increase of computing power allow Large Eddy Simulation (LES) to be applied to real cold flow industrial applications. However, the detailed simulation of the gas-turbine combustion process remains still prohibited because of its enormous computational cost. Several numerical models have been developed in order to reduce the costs of flame simulations for engineering applications. In this paper, the Flamelet-Generated Manifold (FGM) chemistry reduction technique is implemented and progressively extended for the inclusion of all the combustion features that are typically observed in stationary gas-turbine combustion. These consist of stratification effects, heat loss and turbulence. Three control variables are included for the chemistry representation: the reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the stratification effect is expressed by the mixture fraction. The interaction between chemistry and turbulence is considered through a presumed beta-shaped probability density function (PDF) approach, which is considered for progress variable and mixture fraction, finally attaining a 5-D manifold. The application of FGM in combination with heat loss, fuel stratification and turbulence has never been studied in literature. To this aim, a highly turbulent and swirling flame in a gas turbine combustor is computed by means of the present 5-D FGM implementation coupled to an LES turbulence model, and the results are compared with experimental data. In general, the model gives a rather good agreement with experimental data. It is shown that the inclusion of heat loss strongly enhances the temperature predictions in the whole burner and leads to greatly improved NO predictions. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable A. Donini Flow Turbulence Combust (2017) 98:887-922 computational effort. The implemented combustion model retains most of the physical accuracy of a detailed simulation while drastically reducing its computational time, paving the way for new developments of alternative fuel usage in a cleaner and more efficient combustion.

Proceedings of the Combustion Institute

New laminar burning velocity measurements of 85:15% (by volume) H 2 -CO and H 2 -N 2 mixtures wit... more New laminar burning velocity measurements of 85:15% (by volume) H 2 -CO and H 2 -N 2 mixtures with O 2 -He oxidizer are reported at lean conditions and elevated pressures (1-10 atm). Experiments are conducted using the heat flux method at initial temperature of 298 K. In this technique a near adiabatic flame is stabilized by balancing the heat loss from the flame to the burner with heat gain to the unburnt gas mixture such that no net heat loss to the burner is observed. A new facility was designed for such high pressure burner stabilized flame experiments. The results obtained are compared with five chemical kinetic schemes from literature for syngas mixtures at elevated pressures. Large differences are observed between the kinetic schemes and the experiments which can be attributed to certain key chemical reactions. A study of the kinetics is performed through reaction rate and sensitivity analysis which indicate that a high uncertainty still remains in important reactions that drive the production and consumption of species such as H, HO 2 and OH. For lean mixtures the reaction H + O 2 (+M) = HO 2 (+M) contributes significantly to the deviation of models from the experiments. The present analysis in the lean mixture regime suggests the need for further studies in assessment and modification of rate constants for this reaction.

Proceedings of the Combustion Institute

ABSTRACT CFD predictions of flame position, stability and emissions are essential in order to obt... more ABSTRACT CFD predictions of flame position, stability and emissions are essential in order to obtain optimized combustor designs in a cost efficient way. However, the numerical modeling of practical combustion systems is a very challenging task. As a matter of fact, the use of detailed reaction mechanisms is necessary for reliable predictions, especially for highly diffusive fuels. Unfortunately, the modeling of the full detail of practical combustion equipment is currently prohibited by the limitations in computing power, given the large number of species and reactions involved. The Flamelet Generated Manifold (FGM) method reduces these computational costs by several orders of magnitude without loosing too much accuracy. Hereby, FGM enables the application of reliable chemistry mechanisms in CFD simulations of combustion processes. In the FGM technique the progress of the flame is generally described by a few control variables. For each control variable a transport equation is solved during run-time. The flamelet system is computed in a pre-processing stage, and a manifold with all the information about combustion is stored in a tabulated form. In the present paper, the FGM model is implemented for the analysis of partially premixed non-adiabatic flames, including the effects of differential diffusion. Subsequently, a computational analysis of partially premixed non-adiabatic flames is presented. In this scope, a series of test simulations is performed using FGM for a two dimensional geometry, characterized by a distinctive stratified methane/air inlet, and compared with detailed chemistry simulations. The results indicate that detailed simulations are well reproduced with the FGM technique.

Ercoftac Series, 2000

The accuracy of large-eddy simulation (LES) of a turbulent premixed Bunsen flame is investigated ... more The accuracy of large-eddy simulation (LES) of a turbulent premixed Bunsen flame is investigated in this paper. To distinguish between discretization and modeling errors, multiple large-eddy simulations, using different grid size h but the same filterwidth Δ, are compared with the direct numerical simulation (DNS). In addition, large-eddy simulations using multiple Δ but the same ratio Δ/h are compared. The

Flow, Turbulence and Combustion, 2015

In this report we investigate the performance of particle tracking, exploring the influence of an... more In this report we investigate the performance of particle tracking, exploring the influence of an increasing amount of estimators. Basically, a simple method to determine particle matchings was used. Then, first, temporal extrapolation as well as spatial interpolation are employed. Second, a PIV processing step was incorporated. Tests from simulations show that at relatively high seeding densities the performance was increased with a factor of 4 and 13 for the first and second step, respectively. In a physical experiment of a wake behind a heated cylinder a clear performance improvement in the case of PIV preprocessing was observed.

Journal of Engineering for Gas Turbines and Power, 2014

In the present paper, a computational analysis of a high pressure confined premixed turbulent met... more In the present paper, a computational analysis of a high pressure confined premixed turbulent methane/air jet flames with heat loss to the walls is presented. In this scope, chemistry is reduced by the use of the flamelet generated manifold (FGM) method and the fluid flow is modeled in an large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) context. The reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. A generic lab scale burner for methane high-pressure (5 bar) high-velocity (40 m/s at the inlet) preheated jet is adopted for the simulations, because of its gas-turbine relevant conditions. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort. Furthermore, the present analysis indicates that the physical a...

ABSTRACT In the present paper a computational analysis of a high pressure confined premixed turbu... more ABSTRACT In the present paper a computational analysis of a high pressure confined premixed turbulent methane/air jet flames is presented. In this scope, chemistry is reduced by the use of the Flamelet Generated Manifold method [1] and the fluid flow is modeled in an LES and RANS context. The reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. The interaction between chemistry and turbulence is considered through a presumed probability density function (PDF) approach. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort. Furthermore, the present analysis indicates that the physical and chemical processes controlling carbon monoxide (CO) emissions can be captured only by means of unsteady simulations.